1. Field of the Invention
The present invention relates to an image forming apparatus and an image forming method, and more particularly to a double-sided image forming technique for forming a desired image on both sides of a recording medium.
2. Description of the Related Art
In recent years, inkjet printers are becoming more widely used as data output apparatuses for images, documents, and other forms of data. Inkjet printers drive nozzles or other recording elements provided to a print head in accordance with data, and data can be formed on recording paper or another recording medium by ink ejected from the nozzles.
An inkjet printer moves a recording medium and a print head having a large number of nozzles in relation to each other, and an image is formed on the recording paper by ejecting ink droplets from the nozzles.
Conventionally, inkjet printers have been used as an output medium for small-sized, small-scale printing such as documents with a size of about an A4 sheet of paper in offices, homes, and other locations. Because of advances in high-speed, high-quality printing in recent years, however, it has become possible to print large-sized media of A3 size or larger at high speed, and to print photo-sized, high quality images taken with a digital camera or another electronic camera.
There are also inkjet printers that can be used to print both sides and handle various recording papers so that pamphlets and magazines can be created.
There are also inkjet printers that handle double-sided printing by adopting a method whereby one side is printed, the paper is thereafter reversed, and the other side is printed.
In the inkjet printer described in Japanese Patent Application Publication No. 2000-272111, the apparatus is configured with a first head unit for discharging ink to one side of the conveyed recording paper, and a second head unit for discharging ink to the other side so that an image can be recorded to both sides of the recording paper.
In the inkjet double-sided print method and apparatus described in Japanese Patent Application Publication No. 2003-80688, the apparatus is configured to discharge ink simultaneously from two left and right inkjet apparatuses to two left and right blankets disposed in correspondence with the inkjet apparatuses to form a design, paper is passed between the two blankets, and the design formed on the blankets is transferred to both sides of the paper.
However, the method in which printing is carried out on one side, the paper is reversed, and the other side is then printed is not suitable for high-speed printing because the time normally required to print two pages is needed to print a single page. A mechanism for automatically reversing paper is also required. Furthermore, the image quality is liable to be degraded by ink transfer, soiling, and other drawbacks when printing is carried out on the other side without the ink being adequately fixed on the previously printed side.
In the inkjet printer described in Japanese Patent Application Publication No. 2000-272111, it is difficult to assure positional accuracy between the two head groups and the recording medium depending on the quality and thickness of the printing medium. Also, it is impossible to ignore force applied in the gravitational direction because at least one of the head groups does not discharge downward, and it becomes difficult to match the image conditions between the front and reverse sides.
In the inkjet double-sided print method and apparatus described in Japanese Patent Application Publication No. 2003-80688, there is a possibility that ink will not be stably transferred and fixed on the paper, and the quality of the resulting image is liable to considerably vary depending on the type and thickness of the paper.